Portable space heater and gas burner for the same

ABSTRACT

A gas burner to be swept by a high velocity air stream has a cup-shaped primary combustion chamber opening forwardly to a coaxial, annular, radially outwardly opening secondary combustion chamber. The primary combustion chamber has a gas inlet in its closed rear end and air inlets in its cylindrical side wall. The secondary combustion chamber is defined by a large annular flange on the front of the primary combustion chamber and a smaller coaxial baffle disc spaced forwardly of the flange.

United States Patent Reich 51 Sept. 5, 1972 [54] PORTABLE SPACE HEATERAND GASv 3,574,508 4/1971 Rothaar; ..431/351 BURNER FOR THE SAME2,473,435 6/ 1949 Luzader, Sr. ..431/352 X [72] Inventor: Douglas Reich,Menomonee 3,211,439 10/1965 Fahlberg "1263/19 A Fall W PrimaryExaminer-John J. Camby Asslgneei lz g Propane 1 Attorney-Ira MiltonJones wau ee, 18. 22 Filed: Nov. 30, 1970 1 ABSTRACT [21] APPL 7 5 A gasburner to be swept by a high velocity air stream has a cup-shapedprimary combustion chamber opening forwardly to a coaxial, annular,radially outwardly [52] US. Cl. ..263/19 A, 431/353 opening secondarycombustion chamben The primary [51] II.- Cl combustion chanqber has a ginlet in its closed rear [58] held of searchwzwllg 126/2 end and airinlets in its cylindrical side wall. The

secondary combustion chamber is defined by a large annular flange on thefront of the primary combustion [56] Rem-em cued chamber and a smallercoaxial baffle disc spaced for- UNITED STATES PATENTS wardly of theflange- 3,160,40l 12/1964 Wollner ..263/19 A 5 Claims, 5 Drawing Figuresmimosa 51912 3,689,040

SHEU 1 0F 3 FIGJ.

iNvzN-roil .Uuuglas R.RE1EZT PKTENTEMEP 5 I972 I 3.689L04Q sum 3 or 3INVENTOR .Duugias R-Rezczh ATTO Y PORTABLE SPACE HEATER AND GAS BURNERFOR THE SAME This invention relates to gas fired portable heating unitssuch as are used for heating buildings that are under construction, andthe invention relates more particularly to a gas burner for such a unitthat is capable of high heat output with substantially no production ofcarbon monoxide.

In order not to delay construction work during the cold weather season,it has become a practice to use portable heating units to heat theinteriors of unfinished buildings, thus enabling the construction crewsto do their work comfortably and efficiently and also making it possibleto apply certain materials, such as plaster and paint, that cannot beused at temperatures at or near the freezing level.

In most cases the heating units employed for this purpose are fired witha gaseous fuel. Because such heaters must be readily transportable fromone building site to another, they cannot be connected with chimneys orthe like, and therefore they are usually so constructed and arrangedthat they discharge products of combustion into the enclosure to beheated. It will be immediately apparent that any such heater musttherefore provide for very complete combustion of its fuel, forotherwise the products of combustion that it discharges will includecarbon monoxide, which is not only extremely toxic but is colorless andodorless and therefore gives no warning of its presence.

For best efficiency a stream of air should be forced across the gasburner or combustion chamber of such a heater, to effect the bestpossible distribution of heat 'within the space to be heated. At leastfor the larger heating units used for projects such as theaters,shopping center malls and the like, the gas burner is usually mounted ina tubular housing, and air is circulated through the housing by means ofa fan mounted near one end of it. If heat output is high, there must bea correspondingly high volume of air circulated through the tubularhousing per unit time, and this requires that the air move through thehousing at a high velocity. But with prior gas burners, a high velocityair flow over and around the burner interfered with combustion and thuscaused the burner to produce carbon monoxide, or even prevented theburner from operatin g by literally blowing out its flame.

With the above stated considerations in mind, it is a general object ofthe present invention to provide a burner for gaseous fuel that iscapable of achieving complete combustion even when it is mounted in avery high velocity airstream.

It follows that it is also an object of this invention to provide a gasfueled portable space heater that is especially well suited for heatingvery large enclosures by reason of its having a high capacity fan and aburner that is capable of high heat output with complete combustion,even in the presence of the high velocity air stream generated by thefan.

A further object of this invention is to provide a space heater of thetype comprising a tubular housing, a fan mounted in the housing to moveair therethrough, and a burner forvgaseous fuel, also mounted in thehousing, which heater is capable of heat outputs on the order of 750,000Btu/hr. and, by reason of high rates of air flow through its housing,insures that the heat which it produces will be adequately circulatedthroughout a large enclosure.

Another and very important object of this invention is to provide aportable space heater and a gas burner therefor that are capable of highheat output and good distribution of the generated heat, all withoutproduction of such an amount of carbon monoxide as is measurable withthe usually employed detecting instruments.

With these observations and objectives in mind, the manner in which theinvention achieves its purpose will be appreciated from the followingdescription and the accompanying drawings, which exemplify theinvention, it being understood that'such changes may be made in thespecific apparatus disclosed herein as come within the scope of theappended claims.

The accompanying drawings illustrate two complete examples of theembodiments of the invention constructed according to the best modes sofar devised for the practical application of the principles thereof, andin which:

FIG. 1 is a more or less diagrammatic longitudinal sectional view of agas fired portable heating unit embodying the principles of thisinvention; I

FIG. 2 is a longitudinal sectional view through the gas burner of theheating unit of this invention;

FIG. 3 is a view in front elevation of the gas burner, with portions ofthe baffle broken away;

FIG. 4 shows the gas burner in rear elevation; and

FIG. 5 is a view generally similar to FIG. 3 but illustrating a modifiedembodiment of the burner, adapted to burn a different kind of gas.

Referring now to the accompanying drawings, the numeral 5 designatesgenerally a portable space heater which embodies the principles of thisinvention and which comprises, in general, a tubular housing 6, a fan 7that is mounted in the housing, and a burner 8 for gaseous fuel,connected by means of a duct 9 with a source of such fuel, illustratedas a pressure vessel 10.

In order to achieve a high heat output, the burner 8 must consume alarge volume of gas per unit time; and in order to afford adequatecirculation of the heat produced, as well as to provide sufficient airfor complete combustion of the gas, the fan 7 must have a high capacity.For compactness of the unit, as well as for efficiency, the diameter ofthe housing 6 must be limited, and therefore the necessary rate of airflow must be obtained by having the fan force the air through thehousing in a high velocity stream. The burner 8 is capable of achievingcomplete combustion even under the unfavorable conditions created bysuch high speed air flow around it.

Unlike most prior gas burners, which had only a single combustionchamber, the burner 8 of this invention has both a primary combustionchamber 11 and a secondary combustion chamber 12.

The primary combustion chamber is defined by a substantially cylindricalcup-shaped member 13 that is mounted with its axis generally parallel tothe direction of air flow through the housing 6 and with its closed rearend upstream with respect to said direction. The secondary combustionchamber 12, to which the primary combustion chamber opens at its frontend, extends generally in a radially outward direction from the primarycombustion chamber and is defined by an annular flange 14 on the frontend of the cup-shaped member and a coaxial disc-like baffle 15 that isspaced forwardly of the flange.

The cup-shaped member 13 can have its cylindrical side wall 17 formedfrom a length of steel tube, and its end closure or end wall 18 can beprovided by a steel plug or disc welded to the rear end of the tube. Atapped hole 19 in the end wall 18 receives a conventional elbow ornipple 20 that is connectable with the duct 9 through which fuel gas isdelivered into the burner.

The elbow or nipple 20 is in turn internally threaded to receive aninlet nozzle 21 which meters gas into the combustion chamber and bywhich the gas is guided for flow into the chamber in a forward directiongenerally parallel to the axis thereof. Note, however, that the gasinlet is spaced to one side of the axis of the cup-shaped member. It hasbeen found that such eccentric location of the gas inlet is considerablymore favorable to complete combustion than a coaxial position of thenozzle, apparently because the eccentric inlet encourages turbulence inthe incoming stream of gas and thus promotes a more thorough mixing ofthe gas with combustion air. Alternatively, if the nozzle is locatedconcentrically to the cup-shaped member, it can be arranged to directgas into it an an oblique angle to its axis, although this arrangementis less desirable in most cases because it tends to complicateconstruction of the burner.

It has also been found that best results with natural gas are obtainedwith a single relatively large orifice 22 in the nozzle, as shown inFIG. 5, whereas for propane the nozzle should have a plurality ofsmaller, spaced apart apertures 22', as illustrated in FIG. 3.Apparently the heavier propane mixes better with the combustion air ifit is injected into the combustion chamber in several narrow streams.

Air is drawn into the primary combustion chamber through a number ofprimary air inlets 23 in its cylindrical side wall in a zone that isintermediate the front and rear ends thereof. As shown, the primary airinlets comprise a row of holes extending circumferentially around thecup-shaped member.

Between the zone of the air inlet holes 23 and the front end of thecup-shaped member, an igniter 24 projects into the primary combustionchamber from the side wall thereof. The igniter is a conventionalelectrical one and has its electrodes substantially on the axis of thecup-shaped member.

The baffle is supported in forwardly spaced relation to the cup-shapedmember and the annular flange 14 by means of short rods or bars 25 thatextend forwardly from the flange. As illustrated, these comprise bolts32 that extend through aligned holes in the flange and disc and aresecured by nuts 33, and a spacer sleeve 34 surrounding each bolt.

The diameter of the baffle is substantially greater than that of theprimary combustion chamber but substantially less than that of theannular flange 14. The flange is substantially conical and is inclinedforwardly and radially outwardly; or, stated another way, it is dishedand forwardly concave. It can be secured to the front edge of thecup-shaped member as by a weldment 26. The flange has numerous apertures27 therethrough, in annular radially outermost zone thereof, to provideinlets for secondary combustion air. In the case of a burner intended tobe used with propane, the inner boundary of the zone of the secondaryair inlet holes 27 is on a radius approximately equal to that of thebaffle disc. in a burner intended for natural gas, there is preferablyprovided an additional row of smaller secondary air inlet holes 27centered on a circle of approximately the radius last mentioned.

The outer marginal edge portion of the flange comprises a narrow flaredrim 28 that lies in a plane parallel to that of the baffle disc.

When the burner is in operation, gas is of course introduced into theprimary combustion chamber 11 from the inlet nozzle 21, and air is drawninto the primary air inlets 23 to be mixed with the gas. The combustiblemixture is ignited by the igniter 24, and combustion is seen to takeplace through most of the length of the primary combustion chamber, asfar back as a zone spaced a little distance behind the primary air inletholes 23. The only exit for the combusting gases is through the openfront end of the primary combustion chamber, into the secondarycombustion chamber, where the gases impinge against the baffle l5 andare deflected radially outwardly by it. Note that in their radiallyoutward flow through the secondary combustion chamber the combustinggases are accelerated, owing to the convergence of the walls of thatchamber that is afforded by the forwardly dished configuration of theflange 14.

As they issue from behind the baffle l5, flowing rapidly outwardly alongthe radially outermost portion of the annular flange 14, the gases pickup additional combustion air through the secondary air inlets 27. At thesame time, the flange protects the combusting gases from the main forceof the airstream that is blown forwardly over the burner by the fan 7,thus enabling such secondary combustion air to be used for completecombustion.

Careful measurements with conventional carbon monoxide testing deviceshave revealed no detectable output of carbon monoxide from a properlydesigned burner of this invention. In designing a burner embodying theprinciples herein disclosed, as with every new gas burner, someexperimentation may be needed to adjust the sizes of air and gas inlets,the spacing of the baffle disc relative to the flange, and other suchvariables, in order to achieve optimum combustion conditions. However,once the parameters for a burner intended for a particular fuel gas havebeen established, that burner will produce complete combustion over arelatively wide range of gas input rates; hence the heat output of theburner can be regulated to some extent by the mere adjustment of therate of fuel gas flow into the burner.

To aid those skilled in the art in the design of particular burnersembodying the principles of this invention, the following information isgiven concerning the dimensions of a heating unit found to be successfulin use with propane gas and capable of heat outputs of about 350,000 to750,000 Btu/hr.

Housing: Length 48 in.; diameter 21 in.

Fan: Located near inlet end of housing. Motor: l/3 H.P., 1,725 rpm;blade diameter: 20 inches; capacity: 5 ,000 cfm.

Burner: Primary combustion chamber: 2% in. I.D., 5% in. long; in. tappedhole for conventional pipe elbow in rear wall, having its center spacedone-half in. to one side of the chamber axis; inlet nozzle: 3 holes,

equispaced, each about one-sixteenth in. diam., on 5/32 in. radiuscircle; primary air inlet: 8 holes, each eleven-sixteenth in. diam., oncircumferentially equispaced centers about 1 /8 in. forward of the rearwall. Baffle disc: 3 in. radius, 304 stainless steel, spaced about 1%in. from front of primary combustion chamber. Flange: 4% in. radius, 304stainless steel, spaced five-eighths in. rearward of baffle disc at theedge of the latter; A in. outer marginal rim, flared to have its frontsurface lie in a plane parallel to baffle disc and about one-eighth in.behind its rear surface; two rows of 16 circumferentially equispacedgin. diameter holes, one row centered on a 3% in. radius circle, one on a3-5/16 in. radius circle.

Igniter: Fenwall (Div. of Walter Kidde & Co.) catalogue 05-100000-144.

A burner for natural gas, capable of generating 230,000 to 440,000Btu/hr., has the same specifications except that its gas inlet nozzlehas a single 5/16 in. diameter bore and its flange has a third row of 16holes, each about five-sixteenth in. in diameter, circumferentiallyequispaced and centered on a circle of 2% in. radius.

From the foregoing description taken with the accompanying drawings itwill be apparent that this invention provides a burner for gaseous fuelwhich is capable of generating large amounts of heat without productionof carbon monoxide, even in the presence of a high velocity airstreamsweeping across it, and which is thus well adapted for incorporation ina portable gas fired space heater such as is used for buildings underconstruction.

Those skilled in the art will appreciate that the invention can beembodied in forms other than as herein disclosed for purposes ofillustration.

The invention is defined by the following claims:

I claim:

1. A portable heating unit for use with gaseous fuel, comprising:

A. a tubular housing having an air inlet at a rear end thereof and anoutlet at its front end for heated air and combustion products;

B. a fan in said housing for moving air therethrough at a substantiallyhigh velocity; and

C. a burner in the housing, adapted to burn gaseous fuel substantiallywithout production of carbon monoxide despite high velocity of airflowing past it, said burner comprising 1. a generally cylindricalprimary combustion chamber having its axis substantially parallel tothat of the housing, said primary combustion chamber having a rear endwall but being open at its front end, and having a cylindrical side wallthat is apertured for admission of primary combustion air in acircumferential zone which is spaced from its front and rear ends,

2. an eccentric fuel gas inlet in said rear end wall,

communicable with a source of fuel gas,

3. an igniter for the combustion chamber, intermediate its front end andsaid zone,

4. a flat disc-like baffle having a radius substantially greater thanthat of the primary combustion chamber, fixed in forwardly spacedcoaxial relation to the open front end of the primary combustion chamberand providing a surface normal to the axis thereof against whichcombusting gases impinge and by which they are deflected radiallyoutwardly as they issue from the primary combustion chamber, and

5. a forwardly concave conical flange on the front of the primarycombustion chamber having a radius larger than that of the baffle andopposing the same, said flange being spaced rearwardly from the baffleto cooperate therewith in defining a radially outwardly openingcircumferentially extending secondary combustion chamber, said flangehaving circumferentially spaced secondary combustion air aperturestherethrough in an annular zone in its radially outermost portion.

2. The portable heating unit of claim 1, further characterized by:

the fuel gas inlet having its axis substantially parallel to that of theprimary combustion chamber but spaced to one side thereof.

3. A gaseous fuel burner for a portable heating unit of the typecomprising a tubular housing in which the burner is mounted and a fan inthe housing for moving air forwardly therethrough at a high velocity,said gaseous fuel burner comprising:

A. a primary combustion chamber defined by a generally cup-shaped memberhaving a rear end wall, an open front and a substantially cylindricalside wall through which there are primary combustion air inlets in azone spaced from its front and rear ends;

B. an eccentric inlet for gaseous fuel in the rear end wall of saidcup-shaped member;

C. an igniter for said cup-shaped member, intermediate said zone and itsfront end; and

D. means defining a concentric secondary combustion chamber into whichthe primary combustion chamber opens at its front, the last named meanscomprising l. a radially outwardly projecting, forwardly concave,conical annular flange coaxially fixed on the front end of thecup-shaped member, said flange having a radius which is substantiallylarger than that of the cup-shaped member and having secondarycombustion air inlets therethrough in a radially outer annular zonethereof;

2. a flat baffle disc having a radius greater than that of thecup-shaped member but less than that of said flange, and

3. means fixing the baffle disc in forwardly spaced coaxial relation tothe flange and the cup shaped member, with a rear surface of the baffledisc normal to the axis of the cup-shaped member.

4. A gaseous fuel burner adapted to operate in a stream of fast movingair, comprising:

A. a primary combustion chamber defined by a generally cup-shaped memberhaving a closed rear end, an open front end, and a side wall that hasair inlet apertures therethrough, spaced at intervals therearound in azone between its front and rear ends, said cup-shaped member beingadapted for mounting with its axis generally parallel to an air streamand with its rear end upstream;

D. an annular substantially radially extending and ing:

radially outwardly opening secondary combustion chamber into which thefront end of the cupshaped member opens, said secondary combustionchamber being defined by l. a flat baffle disc concentric and normal tothe axis of the cup-shaped member and spaced forwardly from the frontend thereof, the radius of said baffle disc being larger thanthat of thecupshaped member, and

2. a radially outwardly projecting annular flange on the front end ofthe cup-shaped'member having a radius substantially larger than that ofthe baffle disc and having secondary air inlet apertures through itsportion that lies radially outward of the baffle disc, said flange beingsubstantially conical, with a forward and radially outward inclination,but being spaced from the edge of the baffle disc.

A gas burner of the character described, comprismeans defining anelongated primary combustion 8 chamber that is open at a front endthereof, closed at its rear end, and has primary combustion air inletsbetween its ends;

B. means providing an eccentric fuel gas inlet near the rear end of theprimary combustion chamber;

C. means for igniting mixed fuel gas and air in the primary combustionchamber; and

D. means defining a concentric secondary combustion chamber into whichthe primary combustion chamber opens at its front end, the lastmentioned means comprising a pair of opposing spaced apart wall elementsextending in a direction generally transverse to the length of theprimary combustion chamber means but being convergent in said direction,

1. one of said wall elements being a flat concentric disc spacedforwardly beyond the front end of the primary combustion chamber meansand extending entirely across the same, and

2. the other of said wall elements being concentric, conical andforwardly divergent from the front end of the primary combustion chambermeans and having a substantially larger radius than said disc, saidother wall element having secondary air inlets therethrough in acircumferential zone thereof that extends radially beyond said disc andis spaced radially from the primary combustion chamber means.

1. A portable heating unit for use with gaseous fuel, comprising: A. atubular housing having an air inlet at a rear end thereof and an outletat its front end for heated air and combustion products; B. a fan insaid housing for moving air therethrough at a substantially highvelocity; and C. a burner in the housing, adapted to burn gaseous fuelsubstantially without production of carbon monoxide despite highvelocity of air flowing past it, said burner comprising
 1. a generallycylindrical primary combustion chamber having its axis substantiallyparallel to that of the housing, said primary combustion chamber havinga rear end wall but being open at its front end, and having acylindrical side wall that is apertured for admission of primarycombustion air in a circumferential zone which is spaced from its frontand rear ends,
 2. an eccentric fuel gas inlet in said rear end wall,communicable with a source of fuel gas,
 3. an igniter for the combustionchamber, intermediate its front end and said zone,
 4. a flat disc-likebaffle having a radius substantially greater than that of the primarycombustion chamber, fixed in forwardly spaced coaxial relation to theopen front end of the primary combustion chamber and providing a surfacenormal to the axis thereof against which combusting gases impinge and bywhich they are deflected radially outwardly as they issue from theprimary combustion chamber, and
 5. a forwardly concave conical flange onthe front of the primary combustion chamber having a radius larger thanthat of the baffle and opposing the same, said flange being spacedrearwardly from the baffle to cooperate therewith in defining a radiallyoutwardly opening circumferentially extending secondary combustionchamber, said flange having circumferentially spaced secondarycombustion air apertures therethrough in an annular zone in its radiallyoutermost portion.
 2. an eccentric fuel gas inlet in said rear end wall,communicable with a source of fuel gas,
 2. The portable heating unit ofclaim 1, further characterized by: the fuel gas inlet having its axissubstantially parallel to that of the primary combustion chamber butspaced to one side thereof.
 2. a flat baffle disc having a radiusgreater than that of the cup-shaped member but less than that of saidflange, and
 2. a radially outwardly projecting annular flange on thefront end of the cup-shaped member having a radius substantially largerthan that of the baffle disc and having secondary air inlet aperturesthrough its portion that lies radially outward of the baffle disc, saidflange being substantially conical, with a forward and radially outwardinclination, but being spaced from the edge of the baffle disc.
 2. theother of said wall elements being concentric, conical and forwardlydivergent from the front end of the primary combustion chamber means andhaving a substantially larger radius than said disc, said other wallelement having secondary air inlets therethrough in a circumferentialzone thereof that extends radially beyond said disc and is spacedradially from the primary combustion chamber means.
 3. means fixing thebaffle disc in forwardly spaced coaxial relation to the flange and thecup shaped member, with a rear sUrface of the baffle disc normal to theaxis of the cup-shaped member.
 3. A gaseous fuel burner for a portableheating unit of the type comprising a tubular housing in which theburner is mounted and a fan in the housing for moving air forwardlytherethrough at a high velocity, said gaseous fuel burner comprising: A.a primary combustion chamber defined by a generally cup-shaped memberhaving a rear end wall, an open front and a substantially cylindricalside wall through which there are primary combustion air inlets in azone spaced from its front and rear ends; B. an eccentric inlet forgaseous fuel in the rear end wall of said cup-shaped member; C. anigniter for said cup-shaped member, intermediate said zone and its frontend; and D. means defining a concentric secondary combustion chamberinto which the primary combustion chamber opens at its front, the lastnamed means comprising
 3. an igniter for the combustion chamber,intermediate its front end and said zone,
 4. a flat disc-like bafflehaving a radius substantially greater than that of the primarycombustion chamber, fixed in forwardly spaced coaxial relation to theopen front end of the primary combustion chamber and providing a surfacenormal to the axis thereof against which combusting gases impinge and bywhich they are deflected radially outwardly as they issue from theprimary combustion chamber, and
 4. A gaseous fuel burner adapted tooperate in a stream of fast moving air, comprising: A. a primarycombustion chamber defined by a generally cup-shaped member having aclosed rear end, an open front end, and a side wall that has air inletapertures therethrough, spaced at intervals therearound in a zonebetween its front and rear ends, said cup-shaped member being adaptedfor mounting with its axis generally parallel to an air stream and withits rear end upstream; B. a gaseous fuel inlet opening eccentricallyinto the cup shaped member through its closed rear end, said inlet beingconnectable with a source of fuel gas under pressure and arranged toexpel gas forwardly into the cup-shaped member; C. igniter means spacedforwardly of said zone, for initiating combustion of mixed air and fuelgas in the primary combustion chamber; and D. an annular substantiallyradially extending and radially outwardly opening secondary combustionchamber into which the front end of the cup-shaped member opens, saidsecondary combustion chamber being defined by
 5. a forwardly concaveconical flange on the front of the primary combustion chamber having aradius larger than that of the baffle and opposing the same, said flangebeing spaced rearwardly from the baffle to cooperate therewith indefining a radially outwardly opening circumferentially extendingsecondary combustion chamber, said flange having circumferentiallyspaced secondary combustion air apertures therethrough in an annularzone in its radially outermost portion.
 5. A gas burner of the characterdescribed, comprising: A. means defining an elongated primary combustionchamber that is open at a front end thereof, closed at its rear end, andhas primary combustion air inlets between its ends; B. means providingan eccentric fuel gas inlet near the rear end of the primary combustionchamber; C. means for igniting mixed fuel gas and air in the primarycombustion chamber; and D. means defining a concentric secondarycombustion chamber into which the primary combustion chamber opens atits front end, the last mentioned means comprising a pair of opposingspaced apart wall elements extending in a direction generally transverseto the length of the primary combustion chamber means but beingconvergent in said direction,